The conception of social pollution intrinsic to the caste system was contrary to the law of nature. This statement is explained below:

a. Al Biruni wrote the text Kitab ul Hind in which explained about the social life in the Indian Society.

b. According to him, the concept of pollution is intrinsic to the caste system in India was contrary to the law of nature.

c. He explained the caste system as parallels to society.

d. In ancient Persia, four categories were formed.

e. these were of kings and princes, monks, fire priests and lawyers, physicians, astronomers, and other scientists and peasants and artisans.

f. The system of social division is not unique to India.

g. Although he accepted the Brahminical texts, he disapproved of the concept of pollution.

h. He said everything which falls into a state of impurity, strives and succeeds in regaining its original condition of purity.

i. For example, the sun cleanses the air and the salts in the sea prevent the water from becoming polluted.

j. He said that if there was no phenomenon of impurity removal, then life on Earth would be impossible.